aFe 49-48075-B MACH Force-Xp Hi-Tuck 2-1/2 IN 409 Stainless Steel Cat-Back Exhaust SystemaFe 49 48075 B MACH Force Xp Hi Tuck 2 1 2 IN 409 Stainless Steel Cat Back Exhaust System If you want proven performance gains, more ground clearance and sound from your Jeep JL 3. 6L 2 or 4 door, this Mach Force XP cat back exhaust system is what you need. 2 1 2" mandrel bent 409 stainless steel tubing and 14" high flow muffler improves exhaust flow for increased horsepower and torque. In house dyno testing resulted in gains of up to +9 horsepower